1. Field of the Invention:
This invention relates generally to the field of golf clubs and more particularly to their construction and repair. Still more particularly, it relates to a device for repairing damaged faces of, and for improving the ball hitting characteristics of, wooden golf clubs.
2. Description of the Prior Art:
Golf clubs have existed and been in continuous use since the game of golf was invented in Scotland many decades ago. Conventional wisdom suggests that a player use a set of clubs comprising two types: a plurality of "irons" numbered in increasing sequence to reflect shorter shaft lengths and club faces increasingly tilted from the vertical to increase the height of ball flight, and a plurality of "woods" having greater mass and length than irons with a similar but usually smaller array of faces. Irons serve most usefully for shorter shots, usually on the fairway, while woods perform better for greater distances both from the tee and on the fairway.
By far the most important factor affecting ball flight is the skill and strength of the golfer when swinging the golf club. Because of the popularity of the game, however, numerous efforts have been made to improve the hitting characteristics and overall performance of golf clubs in the hands of professionals and amateurs alike. Considerable effort especially has been dedicated to improving the hitting characteristics of woods.
A golf club of the type known as a wood typically has a striking surface, or "face," located on one side of the head. Though the face of a wood appears flat, it is typically curved slightly outward at its center, forming an ideal striking spot, known as the "sweet spot," which theoretically comprises the focal point of all factors affecting ball travel. This curvature of the face exists in both vertical and horizontal planes passing through and intersecting at the sweet spot, the horizontal curvature being known as the "bulge," and the vertical curvature being known as the "roll," of the face. A ten inch radius for both bulge and roll is considered standard, though each may range from 8 inches to 14 inches.
The intended ball flight direction normally will be an extension of an imaginary line through the center of gravity of the club head and exiting the club face at the sweet spot. This imaginary line, or "strike line," is substantially perpendicular to the club shaft and parallel to the bottom, or "sole," of the club head, and it is normal to a vertical projection of the face in an imaginary plane formed perpendicular to the sole. This imaginary plane is ordinarily oriented at a predetermined angle relative to the shaft that takes into account shaft flex during the swing. An "open" faced club's imaginary plane deviates from a parallel orientation relative to the shaft whereby its toe edge is closer to the unflexed shaft axis than its heel edge. A "closed" club face has its heel edge closer to the shaft axis than its toe edge.
Deviation in the tilt of the club face from its vertical projection defines the "loft" of the club face. Increased loft induces greater height into the flight path of the ball above the ground. Standard loft for a "driver," the largest wood used for the longest, flattest ball flight arc, is 11 degrees, though loft may range from 7 or 8 degrees up to 13 degrees. Wood sets typically have 2-3 degrees of additional loft on successive clubs.
Surface rebound characteristics of the club face also affect ball flight, especially in the vicinity of the sweet spot. A trapezoidal shaped wedge of material called an "insert" usually is inlaid into the face covering the region around the sweet spot. An insert allows the manufacturer to provide what that manufacturer considers ideal sweet spot characteristics. Typically, the face will be striated to increase friction in all potential ball contact points using horizontal grooves across the entire face, including the insert.
A spectrum of theories exists about the ideal makeup of the insert. Insisting that the insert should be softer than the rest of the club, patents expound methods and materials to achieve such inserts, typified by Homma, U.S. Pat. No. 4,812,187, and McKee, U.S. Pat. No. 4,804,188. Orlowski illustrates the contrary theory in U.S. Pat. No. 4,749,197, which claims a titanium insert harder than the typical wooden golf club head, thereby imparting additional impetus to the ball derived from the increased elasticity of the strong metal surface. Further, though it is known in the art to resurface the entire face of a club with a plate intended to harden or soften hitting characteristics of more than just the sweet spot (Jepson discloses just such an approach in U.S. Pat. No. 3,937,474), it would be useful to a club manufacturer to have a more efficient means for altering the surface characteristics of club faces.
The ideal golf swing forms an arc to which the strike line forms a tangent touching the swing arc at the sweet spot. If the strike line continues through the center of gravity of the golf ball when the ball is struck by the club face, the ball travels in a flight arc above the ground. This arc lies in a plane defined by the strike line and a "loft line" normal to the tilted club face, the loft line also radiating from the sweet spot. Because of the angle between the sole and the club shaft, known as the "lie" of the club, this ball travel plane should be vertical even though the swing arc is not. Assuming no crosswind, the golfer can theoretically forecast the ball's direction of travel as the intersection of the ball travel plane with the ground. In other words, the projection of the flight arc onto the ground defines the direction of travel along the fairway of the golf ball in flight.
The foregoing also assumes no horizontal ball spin. The ideal swing causes the club face to strike the ball without inducing any horizontal spin in the ball during flight. Horizontal spin occurs where the tangent to the swing arc is not perpendicular to the vertical projection of the club face. Assuming the golfer does not intend such an effect, it usually occurs when the golfer fails to hold the club properly or lets it slip in his hand during his swing. If the club face were turned such that the tangent of the arc were again normal to the club face, the ball would travel in a different direction than intended, but it would still travel in a vertical arc. In the horizontal spin problem, however, the club face remains perpendicular to the intended line of travel, but the swing arc traverses the intended line of travel rather than aligning with it.
The ball begins its flight in the proper direction, but horizontal spin induces a horizontal curve into what should otherwise be a flat, vertical arc above the ground. The ground projection of this horizontal curve is an arc deviating to the left or right of the intended ground line travel direction. Assuming the golfer uses right handed clubs, the intended direction of ball travel lies to the golfer's left, and the face is oriented substantially to his left, when the golfer addresses the ball in preparation for swing. As the golfer begins, he swings the club head to his right and over his right shoulder to a point, then begins a forward swing arc designed to strike the ball with the club face exactly at the sweet spot. A forward swing arc that begins too close to the golfer will cross the intended ball travel line behind the ball and in a direction away from the golfer, thereby inducing counterclockwise spin (as viewed from above) that causes the ball to "hook" to the left of the intended direction of travel. Conversely, a "slice" occurs when the clockwise horizontal spin is induced by a swing arc begun too far away from the golfer.
Golfers occasionally break or bend the shaft of their favorite club, or they wish to increase or decrease shaft flex to achieve better performance. When changing shaft flex of an existing club, the repairs must take into account any shift in face orientation resulting from the new shaft. As the golfer begins his forward swing, the shaft bends into a curvature with the head trailing the unflexed shaft axis. As the swing continues, this curvature straightens out due to the resilience of the shaft itself. At the moment of impact with the ball, the head may have actually caught up with or even passed the shaft axis depending upon the speed and strength of the golfer's hands throughout the swing. At the moment of impact with the ball, the club head should be traveling at its greatest speed, and the shaft should remain flexed in an amount which presents to the ball the face oriented perpendicular to the intended direction of ball travel.
To achieve such proper presentation, the face must be open or closed sufficiently from a parallel orientation relative to the shaft. If a repairer has changed shaft flex, he probably will need to shift the face orientation accordingly. This usually requires "refacing," or sanding down the face to open or close it relative to its original configuration. The adjustment is an irrevocable judgment call when sanding removes wood from the face. A need thus exists for a more efficient means for adjusting a face that is not irrevocable and that simplifies incremental refacing adjustments.
In some golfer's hands, a given golf club consistently produces a hook or a slice. In fact, in some golfers' hands, any club consistently does so. Obviously, it would be preferable for such golfers to relearn what may be long established swing habits to correct whatever error they consistently make. Such efforts do not always meet with complete success, however, and equipment alterations sometimes achieve what tutoring cannot. Consequently, a need often arises for a means for modifying a golf club to counteract undesired tendencies of the club in a given golfer's hands. A golfer may desire alterations to offset hook or slice tendencies, or to change the loft of his existing club.
A golf club may also be custom manufactured with a "hook face" or a "slice face" to offset a slice or hook habit of a given golfer. Ordinarily, a club manufacturer purchases a wooden club head "blank" having the general shape of a wood club, including a face already cut to a given loft. The manufacturer fabricates and installs the sole plate, obtains and installs the insert, including routing a recess for the insert unless the club blank was purchased at extra cost already routed, and drills the "hosel" where the shaft attaches. Variations in each of these fall within the club manufacturer's discretion in light of the type of club he produces or for whom he makes it. If he wishes to alter the loft, hook or slice characteristics of the club head blank, the club manufacturer must drill the hosel at different angles to orient the face accordingly.
Such drilling, however, is limited in scope and usually must be supplemented with sanding the face. Sanding itself can create problems, especially where a hook face is sought, because the heel edge of the face must be cut away to shift the effective plane of the face to a more closed angle. A common hazard in this process is the likelihood of cutting into the hosel, creating a weak point in the club. The process usually requires a skilled craftsman performing a tailored job. A need exists for a device to shift the face angle as a separate step to greatly simplify drilling the hosel. Further, a need exists for a device that relieves the manufacturer of the need for sanding to achieve the proper face angle, to speed the manufacturing process and to reduce the risk of weakening the club.
Through use, woods frequently suffer from damage. Ideally, the ball will be struck at the center of the sweet spot, but more frequently than not, other parts of the club face become involved in a shot. The club head may strike the ground or other hard objects near the ball. Damage can take the form of nicks and erosion of the shape or finish of the golf club around the perimeter of the head. With age, wooden golf clubs dry out, the lacquer finish erodes away, grooves widen, and shrinkage, warping and cracks occur. Such damage lessens the usefulness of the club to the point that it must be replaced. This can be quite expensive in the case of custom clubs for experienced golfers, and matching an existing set of clubs with a replacement club can be difficult for any golfer. A need exists for a convenient, inexpensive and reliable means for repairing the face of woods to prevent damage during use, to increase the longevity of a new club, and to extend the life of a used club in need of repair.